Fluorescent lamp providing visible light and dorno rays

ABSTRACT

The fluorescent lamp comprises a bulb and a layer consisting of a first fluorescent substance having the principal luminous spectrum in the visible ray region and a second fluorescent substance having the principal luminous spectrum in the Dorno ray range. The proportion of the first and second fluorescent substances is selected to radiate visible light fluxes and Dorno ray fluxes at a ratio substantially equal to that of the natural day light. The bulb has a thickness about 0.8mm and is composed of a soda-lime glass which does not transmit radiations of the wave length less than 295nm.

United States Patent Shiraishi Oct. 9, 1973 [5 FLUORESCENT LAMPPROVIDING 3,531,677 9/1970 Loughridge 313/221 x VISIBLE LIGHT AND DORNORAYS 3,287,586 11/1966 Bickford 313/109 2,447,210 8/1948 Roberts 313/109[75] Inventor: HirofumiShiraishi,Yokohama-shi, 2,445,692 7/1948 Porteret a1 313/109 Japan 2,362,384 11/1944 Libby 313/221 X [73] Assignee:Tokyo Shibaura Electric C0.,Ltd., p i p C Demeo K k nhm AttorneyRobertD. Flynn et a1.

[22] Filed: June 2, 1972 211 Appl. No.: 259,180 1 71 R T RltdU.S.A l1 tiDt 63 C ff? 2 ca on a a The fluorescent lamp comprises a bulb and alayer 1 ommumon'm'pan 0 May consisting of a first fluorescent substancehaving the 1970, abandoned.

principal luminous spectrum in the visible ray region and a secondfluorescent substance having the princi- [30] Foreign Apphcauon PnomyData pal luminous spectrum in the Dorno ray range. The May 8, 1969 Japan44/34809 proportion of the first and Second fluorescent stances isselected to radiate visible light fluxes and [52] US. Cl. 313/109, 313/221 -Dorno ray fluxes at a ratio substantiallyequal to h [51] It. Cl"01161/30, H01] 61/44 of the natural day light. The bulb has a thickness[58] Field Of Search 313/109, 221 about 0 and i composed f d glass whichdoes not transmit radiations of the wave length [56] References Citedless than 295nm UNITED STATES PATENTS 3,114,067 12/1963 Henderson313/109 6 2 Drawmg 2,563,900 8/1951 Wollentin et 211.. 3,581,137 5/1971Arnott et a1. 313/109 PATENIEDBBT 9W 3.164.840

500 WAVE LENGTH (nm) 3N0 a0 BONVLSIO v N Luo/Mn NI AilSNlLNI Nouvmvawnaiaads FIG.

.FIG.

FLUORESCENT LAMP PROVIDING VISIBLE LIGHT AND DORNO RAYS CROSS-REFERENCETO RELATED APPLICATION This application is the continuation-in-part ofthe application'Ser. No. 34,848, filed May 5, 1970, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to fluorescent lampsand more particularly to fluorescent lamps emanating Dorno rays.

Ultraviolet rays having a wave 280 to 3l0nm are generally termed ashealth rays or Dorno rays. It is well known in the art that ultravioletrays in this particular range of wavelength manifest the erythemafunction, and act to.conv.ert ergosterol to vitamin D and to enhancerenewal of mineral substances in the human body. The Dorno rays arecontained in natural light in a small quantity (less than I percent ofthe total energy throughout the ranges of ultraviolet rays and visiblerays) and are usuallyabsorbed'by'the human body through exposed portionsof the skin when a man takes a sun-bath or works in the outdoor, thuscontributing to his health. When'a man does not absorb the-Dorno raysover an extendedperiod of time favourable growth of the body is'hindered. In addition unsatisfactory renewal of the mineral results inthe-repture of the vital function thusdecreasing .resistance of the bodyagainst cold and disease. Accordinglyfor men who have little chance ofenjoying a sun-bath owing to their indoor works it is necessaryto givethemthe op- .portunity to absorb'Dorno rays.

Compensation for adverse effects to vital body function may beaccomplished by taking nutritive foods or medicines, but the efficiencyof absorbing them is different from man to man and the absorptionfunction is limited to particular organs. Furtherv the effect of thesenutritive foods or medicines is'temporary.

It is therefore reasonable to irradiate the human body with a suitablequantity of Dorno rays under a prescribed program so as to utilize thevital reaction of'the human body to realize overallcontinuousphysiological effect.

' Health fluorescent sun lamps have been developed to radiate Dorno raysat a high efficiency but such lamps radiate only bright line spectrum ofmercury in the visible range. For example, with a 20-watt health rayfluorescent sun lamp, the luminous flux at .a point one meter spacedapart from the lamp is only about luxes so that it is impossible to usethis lamp for general lighting use. Accordingly,where healthvrayirradiation isrequired in addition to the artificial illumination, forexample in indoor, underground room, enclosed room, or the like, it isnecessary to use ordinary. fluorescent lamps together with such healthray-fluorescent sun lamps in order to keep the health'of men workingunder such an environment over a long time. This requires luminaires forboth types of fluorescent lamps. In addition, conventional fluorescentsun lamps are expensive because they require glass tubes of aspecialcomposition which does not transmit light of thewave length of less than280nm. Further, ashealth ray fluorescent sun lamps radiate a largequantity of Dorno rays their'distribution is not uniform and results inexcessive irradiation. These lamps require an accurate control ofirradiation time. To prevent damage to the skin and to avoid lengthranging from adverse effect on the physiological effect it is necessaryto mount the health ray fluorescent sun lamps at high positions or tocontrol the operation time thereof.

SUMMARY OF THE INVENTION stantially equal to that of the natural daylight.

According to this invention there is provided a fluorescent lampcomprising a bulb having a thickness of 0.7 to 0.9mm and made ofsoda-lime glass intercepting light of a wave length of less than 295nm,the soda-lime glass mainly consisting of SiO,, R,O and R',O bearing '5872, l 2 and 13 18 by parts by weight, a quantity of mercury sealed inthe bulb, electrode means mounted in the bulb, and a fluorescent layerprovided on the inner surface of the bulb, said layer consisting of afirst fluorescent substance having the principal luminous spectrum inthe visible light region, and a second-fluorescent substance having theprincipal luminous spectrum in the Dorno ray region, the weight ratio ofthe first and second fluorescent substances ranging from 97:3 to 88:12.The first and second fluorescent substances may be applied as a mixtureor as separate layers'which are laminated or juxtaposed each other.

The reason why, according to this invention, the bulb should be formedof soda-lime glass with a thickness of 0.7 to 0.9mm is for the purposeof unfailingly intercepting the radiation of only light having a wavelength of less than 295nm. If any of these requisite conditions is notsatisfied, then there will not be obtained the abovementioned effect.For instance, where the bulb has a thickness of less than 0.7mm, lighthaving a wave length of less than 295nm will be emitted. Converselywhere said thickness exceeds 0.9mm, the emission of even the Dorno rayswill be obstructed.

Therefore, the bulb constructed as described above and the prescribedweight ratio of the first to the second fluorescentsubstance naturallyhave a'close interrelationship. In other words, the material and wallthickness of the bulb and the ratio in which the first and secondfluorescent substances are blended together constitute importantparameters in order to ensure that only light having a wave length ofless than 295nm has its passage intercepted whereas the Dorno'rays areeffectively radiated.

BRIEF EXPLANATION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION:With reference to the accompanying drawing there is shown an embodimentof a low pressure mercury vapour discharge lamp constructed according tothe a teaching of this invention.

The lamp shown in FIG. 1 comprises an elongated cylindrical envelope orbulb 10,-electrodes 11 mounted on the opposite ends of thebulb 10 andbases 12 sealing the opposite openings of the bulb. The bulb 10 has athickness of 0.7 to 0.9mm, and preferably of about 0.8mm, and is made ofa soft glass or soda-lime glass having a composition shown in Table 1below, which does not transmit lights of the wave length of less than295nm.

TABLE 1 Ex. l Ex. 2 Ex. 3 SiO, 72 58 69.9 R,O,(AI,O,+ Fe,0,) 2 1 1.98C210 6 0.4 MgO 3 0 3.5 R',0(Na,0+ I90) 17 13 17.32 PhD 0 28 0 As ,0, 0 00.9 Sb,0, 0 0 0.49

In the table, the composition is represented by parts by weight.

On the inner surface of the bulb is applied a fluorescent layer 13comprising a fluorescent substance having the principal luminousspectrum in the range of visible light and a fluorescent substancehaving the principal luminous spectrum in the region of the Dorno rays.The former fluores-cent substance may be calcium halophosphate activatedby antimony-manganese while the latter fluorescent substance may bezinccalcium phosphate activated by thallium. The weight ratio of theformer to the latter fluorescent substance is 96:4, preferably from 97:3to 88:12. The layer 13 may be formed of a single layer comprising themixture of said different fluorescent substances. Alternatively, thelayer 13 may comprise two laminated layers or juxtaposed layers ofdifferent fluorescent substances. Small quantities of mercury and argongas are sealed in bulb 10, the ratio of mercury to argon being equal tothat of the conventional fluorescent lamps. Mercury may be sealed at avapour pressure of 10 l0' mm Hg, for example.

Usually, the quantity of irradiation (does) of Dorno rays is expressedin MPE units. A unit MPE represents the quantity of irradiationeffective to provide minimum noticeable erythema which is produced onthe skin several hours after irradiation of ultraviolet rays butdisappears next day. While the unit MPE is different from one toanother, on the average it amounts to about 0.7E-Viton-h/cm. It is knownthat it is required to irradiate Dorno rays of /4 to 1/10 MPE unit perday in order to maintain normal health condition. Irradiation of 2 MPHunits results in considerable sun-burn while irradiation of excessiveunits of Dorno rays not only results in inflammation of the skin and eyebut also causes side effects such as tire, heartacceleration or thelike.

The quantity of Dorno rays emanated from the fluorescent lamp of thisinvention amounts to about 1.4 X 10 E-Viton in a 40-watt health rayfluorescent lamp containing 6 percent by weight of the fluorescentsubstance and operating in the Dorno ray region. When this lamp isoperated with an illuminating fixture with a white reflecting surfaceand utilized for conventional lamps the intensity of irradiated Dornorays is 0.01 E-Viton'h/cm at a point where the intensity of the visiblelight emanated from the novel lamp is 500 luxes, which is a standardvalue preferred for ordinary operations. At this point the workman willreceive a total of 0.08 E-Vitonh/cm during his working time of 8 hours,for example, thus receiving a suitable quantity of Dorno rays (about l/9MPE) required for maintaining his health. Where intensity of the visiblelight is increased to 2,000 luxes as preferred by the illuminationstandard, the quantity of Dorno rays irradiated during the working timeof 8 hours, for example, will be about k MPE. Such a quantity ofirradiation of the Dorno rays does not cause sun-burn of human skin eventaking into consideration the personal difference in the sensitivity ofthe human body to ultraviolet rays.

Above described embodiment of this invention radiates a qtat i ht s929JP 911IJP Providing cntill imiqal qn 9r va q exat p s- Describing inmore detail, the horizontal light intensity of the natural light (sunlight plus heaven light) at noon in a fine day in midsummer is typicallyabove 92,000 luxes while the Dorno rays amount to about 2 E-Viton/cm(from Luckiesh data, in U.S.A.). According to the measurement in thecity of Kawasaki, Japan, at 1 P.M. on a fine day in May, the intensityof the Dorno rays which was determined from the measured values of thespectrum distribution of the natural light multiplied by the rate oferythema was about 0.5 E- Viton/cm The intensity of the horizontalillumination at that time was about 50,000 luxes.

The intensity of the Dorno rays in the same ratio as the natural lightwas determined to be about 0.022 E-Viton/cm from the former and to beabout 0.01 E-Viton/cm from the latter respectively, where the intensityof illumination was 1,000 lumens.

In contrast, with the above described embodiment of this invention, theintensity of the Dorno rays was about 0.02 E-Viton/cm at portions of theintensity of illumination of about 1,000 luxes.

From this it will be clear that the lamp embodying this invention canprovide the same ratio of visible light flux to Dorno ray flux as thatof the outdoor natural light on fine days.

FIG. 2 shows a spectrum distribution of one embodiment of thisinvention, the ordinate representing the spectrum radiation intensity in;.tW/cm of respective wave lengths at a distance of one meter while theabscissa the wave length in mm.

As can be clearly noted from FIG. 2, there is an appropriate andeffective radiation output in the Dorno ray region and yet the lamp hasa sufficiently large light output and a suitable spectrum distributioncharacteristic in the visible range.

As described above, the envelope of the lamp has a thickness of about0.7 to 0.9mm and is made of soft glass or soda-lime glass which does nottransmit ultraviolet rays of the wave length of less than 295nm. Where ahuman body is exposed over a long time to radiations of high luminousintensity emanated from the lamp of this invention, no physiologicaltrouble is caused by the irradiation of ultraviolet rays of short wavelength.

As described above, it is advantageous to select the proportion ofincorporation of the fluorescent substance having the principal luminousspectrum in the Dorno ray region to be from 3 to 12 percent, by weight,based on the total quantity of the fluorescent substances. With aquantity less than 3 percent, radiation of the Dorno rays becomes verysmall so that health ray radiations are very small. Whereas the quantityexceeds 12 percent, by weight, the quantity of health rays becomesexcessive so that irradiation over a long period at a high luminousintensity is detrimental to health. Further, the visible output usefulfor illumination decreases. The effect of this invention is the maximumwhen the quantity of the fluorescent substance emanating theprincipalluminous spectrum in the Dorno ray range amounts to 4 to percent, byweight, based on the total quantity of fluorescent substances.

Thus, this invention provides a novel fluorescent lamp capable ofproviding sufficient and effective quantity of Dorno ray radiationscontributing to the maintenance of the human health without the troubleof sun-burn at a place where the natural Dorno ray radiations from thesun is not available. Further, the novel lamp radiates the Dorno raystogether with light rays suitable for illumination from a singlefluorescent lamp. In addition, as the novel lamp does not radiateultraviolet rays of short wave length no physiological trouble wouldresult.

What is claimed is:

l. A fluorescent lamp for indoor use and emitting Dorno rays inapproximately the same ratio to visible light as does the sun,comprising a bulb having a thickness of 0.7 to 0.9mm and made ofsoda-lime glass mainly consisting of SiO R 0 and R' O in the respectiveratios of 58 to 72, l to 2 and 13 to 18, based on parts by weight, tointercept the radiation of light having a wave length of less than 295nm through said bulb, wherein R is Al and Fe, and wherein R is Na and K;a quantity of mercury sealed in said bulb; electrode means received insaid bulb; and a fluorescent layer provided on the inner surface of saidbulb, said fluorescent layer consisting substantially of a firstfluorescent substance having a principal luminous spectrum in thevisible light region, and a second fluorescent substance having aprincipal luminous spectrum in the Dorno ray region, and the weightratio of the first to the second fluorescent substance ranging between97:3 and 88:12.

2. The fluorescent lamp according to claim 1 wherein said layer consistsof a mixture of said first and second fluorescent substances.

3. The fluorescent lamp according to claim 1 wherein said firstfluorescent substance comprises calcium halophosphate activated byantimony-manganese and said second fluorescent substance compriseszinc-calcium phosphate activated by the thallium.

4. The fluorescent lamp according to claim 1 wherein the soda-lime glasscomprises SiO R 0 CaO, MgO and R' O bearing the ratio of 72:2:623217based on parts by weight.

5. The fluorescent lamp according to claim 1 wherein the soda-lime glasscomprises SiO R 0 R O and PbO bearing the ratio of 58:1:13228 based onparts by weight.

6. The fluorescent lamp according to claim 1 wherein the soda-lime glasscomprises SiO R 0 CaO, MgO, R' O, As O and Sb O bearing the ratio of69.9:1.98:0.4:3.5:l7.32:0.9:0.49 based on parts by weight.

2. The fluorescent lamp according to claim 1 wherein said layer consistsof a mixture of said first and second fluorescent substances.
 3. Thefluorescent lamp according to claim 1 wherein said first fluorescentsubstance comprises calcium halophosphate activated byantimony-manganese and said second fluorescent substance compriseszinc-calcium phosphate activated by the thallium.
 4. The fluorescentlamp according to claim 1 wherein the soda-lime glass comprises SiO2,R2O3, CaO, MgO and R''2O bearing the ratio of 72:2:6:3:17 based on partsby weight.
 5. The fluorescent lamp according to claim 1 wherein thesoda-lime glass comprises SiO2, R2O3, R''2O and PbO bearing the ratio of58:1:13:28 based on parts by weight.
 6. The fluorescent lamp accordingto claim 1 wherein the soda-lime glass comprises SiO2, R2O3, CaO, MgO,R''2O, As2O5 and Sb2O3 bearing the ratio of69.9:1.98:0.4:3.5:17.32:0.9:0.49 based on parts by weight.